DRV2667: Current Limit and Signal Clipping

Farrell Brown

Part Number: DRV2667
Other Parts Discussed in Thread: DRV2700, DRV2700EVM-HV500

Hello,

I am using the DRV2667 as a voltage-controlled source to create the waveform below. I have the driver programmed to 50Vpp (Gain 01 with recommended resistors) with a boost current limit of 1.8A (Rext = 7.87kohm). Each output trace contains a 600ohm ferrite bead and a 100ohm resistor. When I set the output to the maximum intensity using a 1000ohm load, I get a Vpp of ~72v, but the signal is degraded. The rms current at this intensity is about 18mA. Is the current saturating to cause the distortion? How can I stop the distortion of the signal? Is there a way to boost the output rms current to 40mA?

Thank you!

over 4 years ago

0 Luis Fernando Rodriguez S. over 4 years ago

TI__Guru* 84915 points

Hi, Farrell,

Welcome to E2E and thank you for your interest in our products!

Do you have details about the inductor that you are using? As mentioned in the 7.3.9 section of datasheet, a distortion issue at the output waveform can be related to a low inductor satuation.

http://www.ti.com/lit/ds/symlink/drv2667.pdf#page=12

Could you also provide your circuit schematic to have a better approach to this issue?

Thank you.

Best regards,
Luis Fernando Rodríguez S.

0 Farrell Brown over 4 years ago in reply to Luis Fernando Rodriguez S.

Prodigy 50 points

Hello Luis,

I am using https://www.digikey.com/product-detail/en/murata-electronics-north-america/1277AS-H-3R3M=P2/490-10593-1-ND/6164579 for the inductor. Here is my schematic:

Thank you!

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Farrell Brown

TI__Guru* 84915 points

Hi, Farrell,

What is the purpose of the ferrite bead and the resistor array? Do you have some captures of the output with the ferrite bead and the 100ohms resistor removed? Do you get the same results? Also, are you using a capacitor load or a resistor load?

Best regards,
Luis Fernando Rodríguez S.

0 Farrell Brown over 4 years ago in reply to Luis Fernando Rodriguez S.

Prodigy 50 points

Hello,

The ferrite bead is used to reduce coupling that occured during EMC testing. The 100ohm resistors create a known minimum load resistance and protect the IC/user in a short circuit situation. The output reaches ~80Vpp and Irms of 22.6mA with a load of 1000ohm. Here is the output without the bead and resistor:

I am using a resistor load.

Thanks!

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Farrell Brown

TI__Guru* 84915 points

Hi, Farrell,

In this case, the output waveform will be degraded since the output load is not a piezo haptics actuator. Using the DRV2667 for another purpose is not recommended.

However, in order to reach the maximum amount of current, I would suggest to modify the Rext resistor to the minimum value (6K).

Best regards,
Luis Fernando Rodríguez S.

0 Farrell Brown over 4 years ago in reply to Luis Fernando Rodriguez S.

Prodigy 50 points

Hi Luis,

Thank you for your help. Do you recommend any similar products that can create a high voltage programmable waveform?

Best,

Farrell

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Farrell Brown

TI__Guru* 84915 points

Hi, Farrell,

The DRV2700 could be an option since it may support up to 1KV output with its flyback configuration. However it doesn't have internal waveform memory. You would need to create the waveform by an external controller.

I suggest to take a look at our DRV2700EVM-HV500. This evaluation module can be used for high-voltage applications. The Piezo Control Console contains a Waveform Builder that can be used to send customized waveforms from the microcontroller to the DRV2700 output.

http://www.ti.com/tool/PIEZO-CONSOLE

http://www.ti.com/lit/ug/slou407a/slou407a.pdf

I hope this helps. Please let me know if you have additional questions or comments on this.

Best regards,
Luis Fernando Rodríguez S.

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DRV2667: Current Limit and Signal Clipping